1. Field of the Invention
This invention relates to an image decoding technique. This invention especially relates to a method and apparatus for decoding coded image data.
2. Description of the Related Art
In recent years digital image culture has become commonplace in our daily life as various information devices such as personal computers, digital cameras and color printers have been introduced into our homes and the number of Internet users has exploded. Image compression technology such as JPEG (Joint Photographic Expert Group) and MPEG (Motion Picture Expert Group) for still images and motion images respectively has been standardized. Image distribution and reproduction have become easy and convenient for users using recording media such as CD-ROM and transmission media such as networks and broadcasting technology based on the aforementioned image compression technology. JPEG 2000 has been announced in the JPEG line of technology. In MPEG also, future target specifications have been planned and discussed. There is no doubt that image processing technology will soon play an important role in improving the functionality of digital devices.
For instance, recent digital cameras give users access to a convenient function of shooting of motion pictures, and are therefore taking over the original province of video cameras. The number of pixels in CCD or charge-coupled devices is of an order of millions and some cameras have the function of a high-speed continuous shoot. Although some users stick to cameras using film, no one can resist the tide of the digitization which is rising as music records are replaced by compact discs.
However, in order that these devices can be further developed as commercial products, functionality, operability and cost must be considered together. The enhancement of functionality demands high operability and low cost. For instance, if a function for the playback of a motion picture or a function for high-speed continuous shooting is provided with a digital camera, the image data compressed and stored into a memory card and so forth must be retrieved, decoded and enlarged in time for display. For this purpose, a high-speed image decoder must be incorporated into the digital camera and therefore it is likely to be disadvantageous in cost, power consumption and in the size of the implementation.